If Drosophila melanogaster, with its unparalleled genetic versatility, is to continue to flourish as a system par excellence for the investigation of problems in eucaryotic biology, then it is vital that information concerning the available genetic raw material be readily accessible to investigators in as complete and up-to-date form as possible. We have had support for the past three years to revise "The Genetic Variations of Drosophila melanogaster" and to produce an updated version of the international cross-indexed Drosophila stock list. The second project has been completed and the first is well underway. The present proposal seeks support for completion of the revision of "The Genetic Variations of Drosophila melanogaster". This volume will contain descriptions and references to the original work on all known genes, chromosome rearrangements, special chromosomes, cytological markers, DNA sequences, and departures from diploidy in Drosophila melanogaster. It will also contain a complete cytogenetic map in which the cytological and/or genetic positions of all genes, rearrangement breakpoints, cytological landmarks, and cloned or otherwise special DNA sequences are indicated. Since publication of the original edition fifteen years of prolific activity on the part of record numbers of investigators have led to an explosion of information that is difficult to contain. Updating the catalogue of this material is crucial to continued rapid progress in Drosophila genetics.